1. Field of the Invention
The present invention relates to an ink-jet recording head for use in an ink-jet printer for recording and imaging characters, graphics, images or the like on a recording medium.
2. Related Art of The Invention
In recent years, personal computers have been pervasive in the multimedia information society, and accordingly, demands for printers have greatly grown. Particularly, the market of an ink-jet printer is being expanded since the ink-jet printer can provide a color printout of high quality at a reduced cost.
The ink-jet printer includes various systems: a system in which mechanical vibration is converted into a pressure wave of ink by the use of a piezoelectric element so as to eject ink droplets; a system in which ink is abruptly heated to generate bubbles, a pressure wave of which ejects ink droplets; and a system in which electrostatic force attracts ink so as to allow the ink to spatter. Among these systems, the system using the piezoelectric element has come to widespread attention while a method for fabricating the piezoelectric element has progressed.
There has been proposed an ink-jet recording head having the configuration shown in FIG. 17 (for example, see Japanese Patent Laid-open No. Hei 2-3311). Here, the directions of a length, a width and a thickness are defined as shown in FIG. 17.
In the ink-jet recording head 101, pressure chambers 106 and cavities 108 are alternately arranged in a piezoelectric ceramics material 102 with a pair of driving electrodes 103 interposed therebetween. Ink supplied from an ink supplying portion 104 to the pressure chamber 106 through an ink introducing portion 105 is ejected from a nozzle hole 107.
In the ink-jet recording head having the above-described configuration, a voltage is applied to the driving electrode 103 interposed between the pressure chamber 106 and the cavity 108, thereby deforming the piezoelectric ceramics material. Ejection energy generated in this way can be propagated only to the pressure chamber adjacent to the deformed piezoelectric ceramics material, so that ink droplets can be simultaneously ejected from the adjacent nozzle.
Consequently, it is possible to independently control ejection of the ink from the nozzles, and further, to provide the ink-jet recording head in which the nozzles are arranged at a narrow pitch.
However, in the conventional ink-jet recording head as shown in FIG. 17, it is necessary to efficiently deform the piezoelectric ceramics material at the portion including the driving electrode in order to eject the ink and to thin the piezoelectric ceramics material between the pressure chamber 106 and the cavity 108 very much.
Therefore, there has arisen a problem that the piezoelectric ceramics material is weak from the structural viewpoint, thereby reducing the strength of the ink-jet recording head. This problem induces the difficulty of handling at the time of fabrication, with an attendant problem of reduced yield.
Moreover, in the structure of the conventional ink-jet recording head as shown in FIG. 17, it is necessary to deform two partition walls serving as driving portions (the piezoelectric ceramics portions including the driving electrodes) in order to eject the ink from one nozzle. Since at least two electrodes need be disposed at one partition wall serving as the driving portion, four electrodes in total are needed for one pressure chamber, i.e., for one nozzle. Expensive metal such as silver, palladium or platinum is used as the material of the electrode, thereby raising the problem of an increase in cost of the ink-jet recording head. Moreover, the increased number of electrodes induces problems that the number of connections to outside driving circuits is increased or that a narrow pitch makes connection to an outside circuit difficult.
Furthermore, with the above-described structure, the pressure chamber to be filled with the ink is constituted of mainly the thin piezoelectric ceramics material. Therefore, the rigidity of the pressure chamber becomes low. Part of the deformation energy generated at the piezoelectric ceramics material including the driving electrode is used to deform the wall of the pressure chamber, thereby raising a problem that efficiency of conversion into the ink ejecting energy becomes low.
Furthermore, if the rigidity of the wall defining the pressure chamber is low, the resonance frequency of the pressure chamber becomes low. Therefore, the ejection repeating frequency cannot be made high, thereby raising a problem of slow drawing.
Additionally, since the dimension of the piezoelectric ceramics material including the driving electrode markedly affects directly vibration characteristics in the ink-jet recording head, a slight error at the time of fabrication affects ejection characteristics, thereby raising a problem that ejection uniformity of the plurality of nozzles is deteriorated so as to degrade the quality of an image.
The present invention has been accomplished in an attempt to solve the above-described problems experienced by the conventional ink-jet recording head. An object of the present invention is to provide an ink-jet recording head in which the strength is high, fabricating yield is high and energy converting efficiency is high.
Furthermore, another object of the present invention is to provide an ink-jet recording head having the nozzle arranging structure capable of forming an image of high quality at high speed in the case where numerous nozzles are aligned in two dimensions.
An ink-jet recording head according to one aspect of the present invention comprises at least one piezoelectric block (A) having an ink pressure chamber communicating with a nozzle for ejecting ink to be supplied from an ink introducing portion, a partition wall serving as a driving portion including a piezoelectric element and at least two electrodes for driving said piezoelectric element, a pressure buffer chamber, and a fixed wall,
wherein piezoelectric block (A) is configured such that said ink pressure chamber, said partition wall serving as the driving portion and said pressure buffer chamber are arranged in this order in the same direction, and
said fixed wall is disposed adjacent to said ink pressure chamber and/or said pressure buffer chamber in reference to said the same direction.
An ink-jet recording head according to another aspect of the present invention comprises at least one piezoelectric block (B) having an ink pressure chamber communicating with nozzles for ejecting ink to be supplied from an ink introducing portion, partition walls serving as driving portions including piezoelectric elements and at least two electrodes for driving said piezoelectric elements, a pressure buffer chamber, and fixed walls,
wherein said piezoelectric block (B) is configured such that a first ink pressure chamber, a first partition wall serving as a driving portion, said pressure buffer chamber, a second partition wall serving as a driving portion, and a second ink pressure chamber are arranged in the same direction,
said fixed walls being disposed adjacent to said first ink pressure chamber and said second ink pressure chamber in reference to said the same direction.
An ink-jet recording head according to still another aspect of the present invention comprises:
at least one piezoelectric block (A) having an ink pressure chamber (A) communicating with a nozzle (A) for ejecting ink to be supplied from an ink introducing portion, a partition wall (A) serving as a driving portion including a piezoelectric element (A) and at least two electrodes (A) for driving said piezoelectric element (A), a pressure buffer chamber (A), and a fixed wall (A); and
at least one piezoelectric block (B) having ink pressure chambers (B) communicating with nozzles (B) for ejecting ink to be supplied from an ink introducing portion, partition walls (B) serving as driving portions including piezoelectric elements (B) and at least two electrodes (B) for driving said piezoelectric elements (B), a pressure buffer chamber (B), and fixed walls (B),
wherein said piezoelectric block (A) is configured such that said ink pressure chamber (A), said partition wall (A) serving as the driving portion and said pressure buffer chamber (A) are arranged in this order in the same direction,
said fixed wall (A) is disposed adjacent to said ink pressure chamber (A) and/or said pressure buffer chamber (A) in reference to said the same direction,
said piezoelectric block (B) is configured such that a first ink pressure chamber (B), a first partition wall (B) serving as a driving portion, said pressure buffer chamber (B), a second partition wall (B) serving as a driving portion, and a second ink pressure chamber (B) are arranged in the same direction, and
said fixed walls (B) is disposed adjacent to said first ink pressure chamber (B) and said second ink pressure chamber (B) in reference to said the same direction.
As described above, according to the present invention, it is possible to provide the ink-jet recording head in which the structural strength is high, the durability is excellent, the low-voltage driving can be achieved owing to the high energy using efficiency, the high-frequency ejection can be achieved owing to the high rigidity of the pressure chamber, the printing of high quality can be achieved by the uniform ejection, the image can be formed at high resolution, and the cost can be reduced.